Over the past year, the Genetics Services Research Unit investigators have been conducting genetic counseling related research within two NHGRI research initiatives: The Multiplex Initiative and ClinSeq. Two studies capitalized on the availability of new genetic technology within the Multiplex Initiative that was conducted within a large health care system in Detroit, Michigan. All participants were offered a multiplex genetic test that assessed risk for eight conditions: type 2 diabetes, osteoporosis, hypertension, coronary heart disease, hypercholesterolemia, skin cancer, lung cancer and colorectal cancer. We aimed to understand participants hypothetical interest in selective return of results as little is known about peoples preferences when choosing among conditions on a multi-disease test. In this ancillary study, 294 healthy insured participants were offered multiplex genetic testing. Data was collected at baseline, during decision-making, and testing. One analysis focused on learning how people integrate attitudes about multiple health conditions to make a decision about genetic testing uptake. Averaging attitudes across diseases predicted test uptake but did not contribute beyond peak attitudes, the highest attitude toward testing for a single disease in the set. Peak attitudes were found sufficient to predict test uptake.These findings support theories suggesting that people use representative evaluations in attitude formation. The implication of these findings for further developments in genetic testing is that the communication and impact of multiplex testing may need to be considered in the light of a bias toward peak attitudes. Another analysis assessed the relationships between worry and perceptions of likelihood and severity across the eight common diseases. Individual and disease variability in worry and perceptions were examined. Between- and within-subjects analyses yielded the following main findings: (1) worry is more closely related to likelihood perceptions than to severity perceptions; (2) severity perceptions add significantly to explained worry variances above and beyond likelihood perceptions; (3) risk perceptions and worries form two clusters: cancer diseases and cardiovascular-metabolic diseases; and (4) variance in risk perception and worry is explained by a combination of between- and within-subjects variances. Risk perception research should attend to severity perceptions, within-subjects variability and inter-disease differences, and to strategies for grouping conditions. In conjunction with an NIH clinical whole genome sequencing study we explored participants preferences for the receipt of different types of their sequence results. We conducted a baseline survey of NIH ClinSeq cohort study participants to assess perceptions of uncertainty, hypothesized to be a key determinant of decisions to learn and use sequence information. We developed a novel scale assessing perceptions of uncertainty specific to genomic sequencing, based on theoretical work on uncertainty and focus groups interviews with study participants. The scale contains 10 items that assess perceptions of the projected effect of uncertainties related to genomic sequence results on ones future health and actions. 473 ClinSeq participants completed the scale prior to making a decision about whether to learn their sequence results. There was a normal distribution in responses with an overall mean uncertainty score of 3.5 (SD 0.58) and high internal consistency (&#945;=0.835). Confirmatory factor analysis revealed three factors related to practical uncertainty, affective responses and trustworthiness of the results. Future use of this scale within this longitudinal study will allow us to identify changes in perceptions of uncertainty over time and how perceptions of uncertainty affect decisions about learning and acting on ones sequence results.